To meet the significant growth in oil and gas demand today, exploration is moving to uncharted, ultra-deep water locations and production is being considered in locations previously considered to be off-limits. Further, much of the existing infrastructure typically operates well beyond its designed capabilities. This overreach creates significant technical challenges in all areas of production; however, no challenge is more difficult than preserving infrastructure integrity.
Corrosion inhibitors are frequently introduced into oil and gas fluids to aid in maintaining infrastructure integrity. Corrosion inhibitors are added to a wide array of systems and system components, such as cooling systems, refinery units, pipelines, steam generators, and oil or gas producing and production water handling equipment. These corrosion inhibitors are geared towards combating a large variety of corrosion types. For example, a common type of corrosion encountered in well bores is acid induced corrosion where the degree of corrosion depends on a multitude of factors. These factors include, for example, the corrosiveness of the fluid, pipeline metallurgy, temperature, time of corrosive fluid contact time, and pressure.
Acids and acid solutions have long been used in the stimulation of oil wells, gas wells, water wells, and similar boreholes. Acid stimulation is performed in wells completed in subterranean formations. Acid stimulation generally falls into two categories: (i) matrix acidizing and (ii) fracturing acidizing. In matrix acidizing the acid flows through the natural permeability and porosity of the formation. In fracturing acidizing, the acid travels primarily through natural or induced fractures in the formation. In both stimulation methods, the well treating acid solutions, usually hydrochloric acid (HCl), mixtures of HCl and hydrofluoric acid (HF), or organic acids (e.g., acetic acid), are pumped through the well tubular goods and injected into the formation where the acid attacks formation materials increasing its permeability to oil and/or gas. To protect the equipment and tubular goods from the corrosive effects of the acid, the well treating acid almost always includes a corrosion inhibitor, frequently referred to as an acid corrosion inhibitor or ACI. The literature suggests the use of additives to extend the effectiveness of the acid corrosion inhibitors, including organic and inorganic halide salts (e.g., cuprous iodide and ammonium iodide) as disclosed in U.S. Pat. Nos. 3,773,465; 4,871,024; 4,997,040; and 7,842,127.
Injection of a high performance inhibitor at the appropriate location and optimum dosage can be extremely effective at reducing corrosion rates, such as on pipe walls. Observing a greater than 95% decrease in corrosion is not uncommon. Performance is typically determined through several techniques, such as electrical resistance probes, coupon measurements, autoclave tests, and inspection readings. In some cases, however, corrosion inhibitor performance may deteriorate over time, particularly in systems that have a tendency to accumulate significant quantities of solids or in systems that have had previous corrosion to the metal surfaces.
Stringent governmental regulations have imposed environmental constraints on the oil and gas producing industry. These regulations have led to the need for new “greener” chemistries, which have reduced environmental impact. The environmental impact of any chemical can be defined, in part, by three criteria: biodegradation, bioaccumulation, and toxicity. All three criteria have benchmarks that must be met for a chemical to be permitted for use (e.g., the North Sea area of operations), with different emphasis on each depending on which regulating body controls the waters. This environmental drive has been spearheaded by North Sea Regulators (e.g., CEFAS) and their success has sparked similar programs, currently being implemented in other oil producing regions. Operators now frequently demand identical levels of performance with existing treatments along with the fulfillment of the new environmental criteria for any chemicals that may be contained, for example, in rig overboard discharge.
In view of these challenges, there exists an ongoing need for improved, and in particular environmentally friendly, corrosion inhibitors. Specifically, corrosion inhibitors having high levels of biodegradability, low potential to bioaccumulate, and low aquatic toxicity while maintaining adequate corrosion inhibition are desirable. Simultaneously protecting a system from corrosion caused by the presence of introduced and naturally occurring acidic species as well as bacterial byproducts would also be highly desirable.